TOKYO, Japan — Following an increase in violence among inmates, prison officials boosted the number of single-occupancy prison cells to almost 47 percent for Japan's 81,000-inmate prison population.

The government began increasing the number of single-bed cells systemwide following a 2003 prison administration panel study that called for the re-examination of inmate housing policies.

By 2006, the number of solitary cells in the system was increased to more than 37,000, according to the Justice Ministry. The ministry plans to expand single-bed cells to about 70 percent, as it continues future expansion of prison capacity nationwide, officials say.